Configuring 802.11 Bands

Configuring 802.11 Bands

Information About Configuring 802.11 Bands

You can configure the 802.11b/g/n (2.4-GHz) and 802.11a/n (5-GHz) bands for the controller to comply with the regulatory requirements in your country. By default, both 802.11b/g/n and 802.11a/n are enabled.

When a controller is configured to allow only 802.11g traffic, 802.11b client devices are able to successfully connect to an access point but cannot pass traffic. When you configure the controller for 802.11g traffic only, you must mark 11g rates as mandatory.

Configuring the 802.11 Bands (GUI)

Select the
802.11a (or
802.11b/g)
Network Status check box
to enable the 802.11a or 802.11b/g band. To disable the band, unselect the
check box. The default value is enabled. You can enable both the 802.11a and
802.11b/g bands.

Step 3

If you enabled the 802.11b/g band in
Step 2,
select the
802.11g Support check box
if you want to enable 802.11g network support. The default value is enabled. If
you disable this feature, the 802.11b band is enabled without 802.11g support.

Step 4

Specify the period at which the SSID is broadcast by the
access point by entering a value between 20 and 1000 milliseconds (inclusive)
in the Beacon Period text box. The default value is 100 milliseconds.

Note

The beacon period in
controllers is listed in terms of milliseconds. The beacon period can also be
measured in time units, where one time unit equals 1024 microseconds or 102.4
milliseconds. If a beacon interval is listed as 100 milliseconds in a
controller, it is only a rounded off value for 102.4 milliseconds. Due to
hardware limitation in certain radios, even though the beacon interval is, say
100 time units, it is adjusted to 102 time units, which roughly equals 104.448
milliseconds. When the beacon period is to be represented in terms of time
units, the value is adjusted to the nearest multiple of 17.

Step 5

Specify the size at which packets are fragmented by
entering a value between 256 and 2346 bytes (inclusive) in the Fragmentation
Threshold text box. Enter a low number for areas where communication is poor or
where there is a great deal of radio interference.

Step 6

Make access points advertise their channel and transmit
power level in beacons and probe responses for CCX clients. Select the
DTPC Support check box.
Otherwise, unselect this check box. The default value is enabled.

Client devices using dynamic transmit power
control (DTPC) receive the channel and power level information from the access
points and adjust their settings automatically. For example, a client device
used primarily in Japan could rely on DTPC to adjust its channel and power
settings automatically when it travels to Italy and joins a network there.

Note

On
access points that run Cisco IOS software, this feature is called
world mode.

Note

DTPC and 801.11h power
constraint cannot be enabled simultaneously.

Step 7

Specify the
maximum allowed clients by entering a value between 1 to 200 in the Maximum
Allowed Client text box. The default value is 200.

Step 8

Use the Data Rates options to specify the rates at which
data can be transmitted between the access point and the client. These data
rates are available:

802.11a—6, 9, 12, 18, 24, 36,
48, and 54 Mbps

802.11b/g—1, 2, 5.5, 6, 9,
11, 12, 18, 24, 36, 48, or 54 Mbps

For each data rate, choose
one of these options:

Mandatory—Clients must support this data rate in order to
associate to an access point on the controller.

Supported—Any associated clients that support this data rate
may communicate with the access point using that rate. However, the clients are
not required to be able to use this rate in order to associate.

Disabled—The clients specify the data rates used for
communication.

Step 9

Click
Apply.

Step 10

Click
Save Configuration.

Configuring the 802.11 Bands (CLI)

Step 1

Disable the 802.11a band by entering this command:

config 802.11adisablenetwork

Note

The 802.11a band must be disabled before you can configure the 802.11a network parameters in this section.

Step 2

Disable the 802.11b/g band by entering this command:

config 802.11bdisablenetwork

Note

The 802.11b band must be disabled before you can configure the 802.11b network parameters in this section.

Step 3

Specify the rate at which the SSID is broadcast by the access point by entering this command:

config {802.11a | 802.11b} beaconperiodtime_unit

where time_unit is the beacon interval in time units (TUs). One TU is 1024 microseconds. You can configure the access point to send a beacon every 20 to 1000 milliseconds.

Step 4

Specify the size at which packets are fragmented by entering this command:

config {802.11a | 802.11b} fragmentation threshold

where threshold is a value between 256 and 2346 bytes (inclusive). Specify a low number for areas where communication is poor or where there is a great deal of radio interference.

Step 5

Make access points advertise their channel and transmit power level in beacons and probe responses by entering this command:

config {802.11a | 802.11b } dtpc {enable | disable}

The default value is enabled. Client devices using dynamic transmit power control (DTPC) receive the channel and power level information from the access points and adjust their settings automatically. For example, a client device used primarily in Japan could rely on DTPC to adjust its channel and power settings automatically when it travels to Italy and joins a network there.

Note

On access points that run Cisco IOS software, this feature is called world mode.

Step 6

Specify the maximum allowed clients that can be configured by entering this command:

config {802.11a | 802.11b} max-clientsmax_allow_clients

The valid range is between 1 to 200.

Step 7

Specify the rates at which data can be transmitted between the controller and the client by entering this command:

mandatory—Clients support this data rate in order to associate to an access point on the controller.

supported—Any associated clients that support this data rate may communicate with the access point using that rate. However, the clients are not required to be able to use this rate in order to associate.

rate—The rate at which data is transmitted:

6, 9, 12, 18, 24, 36, 48, and 54 Mbps (802.11a)

1, 2, 5.5, 6, 9, 11, 12, 18, 24, 36, 48, or 54 Mbps (802.11b/g)

Step 8

Enable the 802.11a band by entering this command:

config 802.11aenablenetwork

The default value is enabled.

Step 9

Enable the 802.11b band by entering this command:

config 802.11benablenetwork

The default value is enabled.

Step 10

Enable or disable 802.11g network support by entering this command:

config 802.11b 11gSupport {enable | disable}

The default value is enabled. You can use this command only if the 802.11b band is enabled. If you disable this feature, the 802.11b band is enabled without 802.11g support.

Step 11

Enter the save config command to save your changes.

Step 12

View the configuration settings for the 802.11a or 802.11b/g band by entering this command:

Information About Configuring Band Selection

Band selection enables client radios that are capable of dual-band (2.4- and 5-GHz) operation to move to a less congested 5-GHz access point. The 2.4-GHz band is often congested. Clients on this band typically experience interference from Bluetooth devices, microwave ovens, and cordless phones as well as co-channel interference from other access points because of the 802.11b/g limit of three nonoverlapping channels. To prevent these sources of interference and improve overall network performance, you can configure band selection on the controller.

Band selection is enabled globally by default.

Band selection works by regulating probe responses to clients. It makes 5-GHz channels more attractive to clients by delaying probe responses to clients on 2.4-GHz channels.

Restrictions on Band Selection

Band-selection enabled WLANs
do not support time-sensitive applications like voice and video because of
roaming delays.

Band selection can be used
only with Cisco Aironet 1040, 1140, 1250, 1260, 1550, 1600,
2600,
3500, 3600,
series access
points.

Note

OEAP 600 Series access points
do not support band select.

Band selection operates only
on access points that are connected to a controller. A FlexConnect access point
without a controller connection does not perform band selection after a reboot.

The band-selection algorithm
directs dual-band clients only from the 2.4-GHz radio to the 5-GHz radio of the
same access point, and it only runs on an access point when both the 2.4-GHz
and 5-GHz radios are up and running.

You can enable both band
selection and aggressive load balancing on the controller. They run
independently and do not impact one another.

It is not
possible to enable or disable band selection and client load balancing globally
through the controller GUI or CLI. You can, however, enable or disable band
selection and client load balancing for a particular WLAN. Band selection and
client load balancing are enabled globally by default.

Configuring Band Selection

Configuring Band Selection (GUI)

Step 1

Choose Wireless > Advanced > Band Select to open the Band Select page.

Step 2

In the Probe Cycle Count text box, enter a value between 1 and 10. The cycle count sets the number of suppression cycles for a new client. The default cycle count is 2.

Step 3

In the Scan Cycle Period Threshold (milliseconds) text box, enter a value between 1 and 1000 milliseconds for the scan cycle period threshold. This setting determines the time threshold during which new probe requests from a client come from a new scanning cycle. The default cycle threshold is 200 milliseconds.

Step 4

In the Age Out Suppression (seconds) text box, enter a value between 10 and 200 seconds. Age-out suppression sets the expiration time for pruning previously known 802.11b/g/n clients. The default value is 20 seconds. After this time elapses, clients become new and are subject to probe response suppression.

Step 5

In the Age Out Dual Band (seconds) text box, enter a value between 10 and 300 seconds. The age-out period sets the expiration time for pruning previously known dual-band clients. The default value is 60 seconds. After this time elapses, clients become new and are subject to probe response suppression.

Step 6

In the Acceptable Client RSSI (dBm) text box, enter a value between –20 and –90 dBm. This parameter sets the minimum RSSI for a client to respond to a probe. The default value is –80 dBm.

In the Load Balancing and Band Select text area, if you want to enable band selection, select the Client Band Select check box. If you want to disable band selection, leave the check box unselected. The default value is disabled.

Step 12

Click Save Configuration.

Configuring Band Selection (CLI)

Step 1

Set the probe cycle count for band select by entering this command:

config band-select cycle-count cycle_count

You can enter a value between 1 and 10 for the cycle_count parameter.

Step 2

Set the time threshold for a new scanning cycle period by entering this command:

config band-select cycle-threshold milliseconds

You can enter a value for threshold between 1 and 1000 for the milliseconds parameter.

Step 3

Set the suppression expire to the band select by entering this command:

config band-select expire suppression seconds

You can enter a value for suppression between 10 to 200 for the seconds parameter.

Step 4

Set the dual band expire by entering this command:

config band-select expire dual-band seconds

You can enter a value for dual band between 10 and 300 for the seconds parameter.

Step 5

Set the client RSSI threshold by entering this command:

config band-select client-rssi client_rssi

You can enter a value for minimum dBm of a client RSSI to respond to a probe between 20 and 90 for the client_rssi parameter.

Step 6

Enter the save config command to save your changes.

Step 7

Enable or disable band selection on specific WLANs by entering this command: